An X-ray CT (Computed Tomography) device is known for generating cross-sectional images of an object. More specifically, a cross-sectional image is generated by producing X-ray beams with an X-ray tube, which is passed through the object and converting the transmitted X-ray into signals that provide basis for generating a cross-sectional image of the object. To produce such image, X-ray CT device is typically arranged to rotate a rotary part, including the X-ray tube and the X-ray detector, relative to a stationary part. Conventionally, in order to transmit power to the rotary part from the stationary part, a slip ring-brush configuration has been employed. However, the slip ring-brush configuration, requiring contact between the components, requires tedious maintenance work to recover component wear-out.
In view of the above concerns, JP 3827335 B discloses an electromagnetic induction transformer comprising a primary side and a secondary side, the primary side being provided at the stationary part and the secondary side being provided at the rotary part. The stationary part converts AC (Alternate Current) voltage provided by commercially available AC power into high-frequency voltage with a DC (Direct Current) power circuit and an inverter circuit. The high-frequency voltage is applied on the primary side. The rotary part, on the other hand, utilizes a high-voltage transformer for further stepping up the high-frequency voltage generated at the secondary side to a required voltage level to be supplied to the X-ray tube. The stepped up high-frequency voltage is rectified by the rectifier circuit, and the rectified DC voltage is applied to the X-ray tube. According to the above described configuration, burden of maintenance checkup for providing non-contact power transmission from the stationary part to the rotary part can be reduced.
The X-ray tube, however, requires application of high voltages ranging from 70 kV to 150 kV. The high-voltage transformer according to the conventional configuration needs to be increased in size in order to provide relatively higher voltages, which in turn leads to increased weight that may amount to 100 kg, for example. Such heavy and sizable high-voltage transformer, when provided at the rotary part, imparts increased centrifugal force upon rotation of the rotary part. Increased centrifugal force consequently requires structural reinforcement of the rotary part which in turn unwantedly causes increase in weight, leaving the problem of increased centrifugal force unsolved. Thus, one may conceive to reduce the maximum rotational speed in order to reduce the centrifugal force. However, maximum rotational speed of the rotary part is a critical factor in determining the quality of images generated by the X-ray CT device, such that when reduced, does not provide improved imaging quality.
Further, when heavy and sizable components are provided at the rotary part, balance of weight of the rotary part becomes unstabilized and may cause unwanted rotational variance. Rotational variance may be restrained by placing a balancer at the rotary part. However this will further increase the weight of the rotary part, which in turn increases the centrifugal force.